These are about $4 at Amazon (via 3rd party sellers.)
Description: Cra-Z-Art Washable Markers will lend creativity to any project. They are non-toxic, making them ideal for children. In addition, any messes will wash right out. Cra-Z-Art markers have broadline tips and come in bright, classic colors.
Excellent reviews (5 star rating): "Low cost markers that are just as good as the competition. Super easy to wash off and didn't stain clothes when daighter decided to color on her shirt instead of the paper."